Add Python 3.13

[bdice]

This PR adds Python 3.13 CI images for ci-wheel and citestwheel.

For now we are blocked by conda-forge/conda-feedstock#246 on adding Python 3.13 support to our conda CI images. However, I went ahead and did some refactoring that will be needed for conda support once that is available.

[jakirkham]

This is now failing as boa requires an older version of conda, which is incompatible with Python 3.13

Sounds like we should prioritize dropping boa to move Python 3.13 forward: rapidsai/build-planning#149

[bdice]

I wrote up an automation script that we can use to convert all RAPIDS repositories from conda mambabuild to conda build, which would allow us to drop boa. However, we are also working through a migration to rattler-build which will effectively drop boa.

Even if we dropped boa, we would still be blocked from migrating to Python 3.13 because cupy doesn't support Python 3.13 yet. cupy/cupy#8651

In the interest of keeping our total work at a minimum: if cupy and other RAPIDS dependencies become available for Python 3.13 but still haven't finished the rattler-build upgrade, then we can migrate all remaining RAPIDS repositories off of boa to unblock the Python 3.13 upgrade.

[bdice]

This should be unblocked now.

[jameslamb]

Double-checked a couple build logs, saw the things I expected... the right build-string filters to say "only give us CPython", the right Python versions installed, and no new warnings to worry about.

I'm ok with duplicating the PYTHON_*_VERSION logic in the Dockerfile instead of doing that in compute-build-args.sh, think that's fine.